1. Field of the Invention
This invention relates generally to low dielectric constant (“low-k”) materials, and more particularly to chemical vapor deposition (CVD) processes for making low-k materials, and the use of low-k materials as dielectric layers in microelectronic devices.
2. Description of the Related Art
As the dimensions of microelectronic devices become smaller, the importance of the physical properties of the materials used in their manufacture becomes more important. This is particularly true of the dielectric materials that are used to insulate metal lines and vias from one another because of the contributions to parasitic capacitance that these materials make. Silicon dioxide has been employed within the industry as a dielectric material for the manufacture of devices for nearly three decades, but may become less suitable in the future because of its relatively high dielectric constant (k˜4.1). Thus, there is a need in the art of microelectronic device manufacturing for a process to deposit low-k films.
Fluorinated silicon glass (FSG) has been identified as a possible replacement for silicon dioxide, see e.g., U.S. Pat. Nos. 5,563,105; 5,703,404; and 5,876,798. FSG films are known to have a dielectric constant in the range 3.3 to 3.6, depending on the fluorine concentration.
Carbon is also known to reduce the dielectric constant of oxide materials. Generally speaking, organic precursors are employed in plasma deposition or spin-on deposition processes. The preparation of low-k films by plasma-enhanced chemical vapor deposition (PECVD) has been disclosed, for example in G. Sugahara et al., “Low Dielectric Constant Carbon Containing SiO2 Films Deposited By PECVD Technique Using a Novel CVD Precursor,” Feb. 10-11, 1997, DUMIC Conference, 97ISMIC-222D; T. Shirafuji et al., “Plasma Copolymerization of Tetrafluoroethylene/Hexamethyldisiloxane and In Situ Fourier Transform Infrared Spectroscopy of Its Gas Phase,” Jpn. J. Appl. Phys., 38, 4520-26 (1999); M. Loboda, “New solutions for intermetal dielectrics using trimethylsilane-based PECVD processes,” Microelectronic Engineering, 50, 15-23 (2000); T. Shirafuji et al., “PE-CVD of Fluorocarbon/SIO Composite Thin Films Using C4H8 and HMDSO,” Plasmas and Polymers, 4(1) 57-75 (1999); T. Shirafuji et al., “PE-CVD of Fluorocarbon/Silicon Oxide Composite Thin Films from TFE and HMDSO,” Mat. Res. Soc. Symp. Proc., 544, 173-178 (1999). Other references in this regard include Indrajit Banerjee, et. al., “Characterization of Chemical Vapor Deposited Amorphous Fluorocarbons for Low Dielectric Constant Interlayer Dielectrics.” J. Electrochem. Soc., Vol. 146(6), p. 2219, 1999; C. B. Labelle, et. al., DUMIC, pg. 1998, 1997; Sang-Soo Han, et. al., “Deposition of Fluorinated Amorphous Carbon Thin Films as a Low-Dielectric Constant Material.” J. Electrochem. Soc., Vol. 146(9), p. 3383, 1999; U.S. Pat. Nos. 6,068,884; 6,051,321; 5,989,998; and 5,900,290. All patents and literature references mentioned herein are incorporated by reference in their entireties.
Spin-on processes are also known for making low-k films. These processes generally involve dissolving or dispersing a low-k polymer in a solvent to form a liquid coating mixture, depositing the coating mixture onto a substrate, spinning the substrate to create a uniform coating, then drying the coating to remove the solvent. Another known method for reducing the dielectric constant of a film is to introduce porosity into the film.
There remains a need for low-k films having better properties more suitable for use in microelectronics manufacturing, and for processes for producing such films that can be readily integrated into fabrication process flows.